Creating sensor from nested attribute values

Am struggling to find the correct syntax to surface the number of errors or the fault codes from this entity.

I have tried variants off the following but to no avail:

{% set bob = state_attr('climate.study', 'active_faults') %}

Returns: None

{% set bob = state_attr('climate.study', 'active_faults')[0].FaultType %}

UndefinedError: None has no element 0

Any help would be appreciated.